/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int sumNumbers(TreeNode* root) {
        return dfs(root,0);
    }

    int dfs(TreeNode* root,int tmp)
    {
        tmp=tmp*10+root->val;
        if(root->left==nullptr&&root->right==nullptr)
            return tmp;

        int ret=0;
        if(root->left) 
        {
            ret+=dfs(root->left,tmp);
        }
        if(root->right)
        {
            ret+=dfs(root->right,tmp);
        }
        return ret;
    }
};
